Abnormalities of resting-state functional cortical connectivity in patients with dementia due to Alzheimer's and Lewy body diseases: an EEG study
Previous evidence showed abnormal posterior sources of resting-state delta (
rhythms in patients with Alzheimer’s disease with dementia (ADD), Parkinson’s disease with dementia
(PDD), and Lewy body dementia (DLB), as cortical neural synchronization markers in quiet wakefulness.
Here, we tested the hypothesis of additional abnormalities in functional cortical connectivity computed
in those sources, in ADD, considered as a “disconnection cortical syndrome”, in comparison with PDD
and DLB. Resting-state eyes-closed electroencephalographic (rsEEG) rhythms had been collected in 42
ADD, 42 PDD, 34 DLB, and 40 normal healthy older (Nold) participants. Exact low-resolution brain
electromagnetic tomography (eLORETA) freeware estimated the functional lagged linear connectivity (LLC) from rsEEG cortical sources in delta, theta, alpha, beta, and gamma bands. The area under receiver
operating characteristic (AUROC) curve indexed the classification accuracy between Nold and diseased
individuals (only values >0.7 were considered). Interhemispheric and intrahemispheric LLCs in widespread delta sources were abnormally higher in the ADD group and, unexpectedly, normal in DLB and
PDD groups. Intrahemispheric LLC was reduced in widespread alpha sources dramatically in ADD,
markedly in DLB, and moderately in PDD group. Furthermore, the interhemispheric LLC in widespread
alpha sources showed lower values in ADD and DLB than PDD groups. At the individual level, AUROC
curves of LLC in alpha sources exhibited better classification accuracies for the discrimination of ADD
versus Nold individuals (0.84) than for DLB versus Nold participants (0.78) and PDD versus Nold participants (0.75). Functional cortical connectivity markers in delta and alpha sources suggest a more
compromised neurophysiological reserve in ADD than DLB, at both group and individual levels